The invention relates generally to a throttle for gaseous fuel control for gaseously fueled engines. Such engines have existed, even in vehicles, for many years, and augmented future reliance is anticipated given the current availability and usage rates of fuel sources such as liquid petroleum gas. Compressed natural gas, used as a substitute for liquid petroleum gas, has several advantages. It is more abundantly found in our environment, it is less expensive to buy the requisite fuel to traverse a given distance, and it is a cleaner burning fuel since there is much less carbon present in the combustion chamber.
The most common gaseous fuel carburetor systems were developed for liquified petroleum gas. If modified to handle the greater flow required for compressed natural gas, these carburetor systems function, but they are undersized, and they produce substandard emissions.
One type of gaseous fuel carburetor is the venturi model where a constricted air passageway causes an increase in air flow rate and a corresponding decrease in pressure. Openings in the venturi throat allow gaseous fuel to be pulled in by the lower pressure flowing air. Such a method is discussed in Dutch Patent No. NL 8603-136-A.
To determine the requirements of the engine, some systems use an air flow transducer to measure the air being used by the engine. These air flow transducers, however, have cost, life and accuracy problems. Others systems "map" the engine and derive air flow from a table of engine characteristics. The engine "map" method may achieve good results if the engine has no variable characteristics, but each installation must be "mapped". Such a system may be adequate for high production volumes, but it definitely limits versatility. Fluidic control systems let the air flow generate a signal or operator that governs gas flow, such as a venturi or air-operated trap door. These systems have tracking and linearity problems.
Hence, there is a need for a gaseous fuel control system which can efficiently regulate and accurately adjust to the needs of the engine.